The invention relates to a balancing circuit for a metal detector. Known metal detectors include an oscillator (or transmit) coil and two detector (or receive) coils. The receive coils are typically positioned on either side of the oscillator coil and substantially equidistant therefrom. The oscillator coil is provided with an oscillatory signal that is inductively coupled to the detector coils. Metal passing through the coils causes an imbalance in the inductively coupled signals, which can be used to detect the presence of the metal.
To operate properly, the inductively coupled signals should be balanced such that the signals produced by each receive coil are the same when metal is not present. Due to variances in tolerances, aging of materials, etc., it is necessary to provide a means of balancing the inductively coupled signals when no metal is present.